Absorbable sponge with contrasting agent

ABSTRACT

An absorbable sponge containing a contrasting agent (e.g, radiopaque agent) that can be introduced to a biopsy tract or other puncture wound site is provided. The contrasting agent permits identification of the site by fluoroscopy or other imaging techniques.

[0001] This application is a CIP of U.S. application Ser. No.09/071,670, filed May 1, 1998 and U.S. application Ser. No. 09/1071,284,filed May 1, 1998.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to an absorbable sponge, and moreparticularly, the invention relates to the delivery of a contrastingagent to a specific area or site in a mammal after a surgical orinterventional procedure. The contrasting agent facilitates the locationof the area or site even weeks or months after the initial procedure.

[0004] 2. Brief Description of the Related Art

[0005] Percutaneous needle biopsy of solid organs is one of the mostcommon interventional medical procedures. Millions of percutaneousneedle biopsies are performed annually in the United States andthroughout the world. Percutaneous biopsy is a safe procedure which hassupplanted surgical biopsy for many indications, such as skin biopsy andliver biopsy.

[0006] Possible complications of needle biopsy include bleeding at thebiopsy site. The amount of bleeding is related to a number of factorsincluding needle size, tissue sample size, patient's coagulation status,and the location of the biopsy site. Vascular organs such as the liver,a common biopsy target, may bleed significantly after needle biopsy.

[0007] Sterile sponges, such as GELFOAM, are prepared in dry sterilesheets which are used as packing material during surgery for control ofbleeding. The sponge sheets are left in the surgical site after surgeryto stop bleeding and are absorbed by the body. A number of techniqueshave used these absorbable sterile sponge materials to plug a biopsytract to minimize or prevent bleeding. The absorbable sponge provides amechanical blockage of the tract, encourages clotting, and minimizesbleeding though the biopsy tract.

[0008] During the biopsy, a mechanic clip device is often attached tothe site where tissue is removed, so that if further treatment is laterrequired the location of the site can be identified. Unfortunately, thetime period between the biopsy and treatment may be weeks during whichtime the clip may become dislodged thereby making it difficult torelocate the site.

[0009] Accordingly, it would be desirable to provide a reliabletechnique for identifying biopsy sites or puncture wound sites.

SUMMARY OF THE INVENTION

[0010] The present invention is based in part on the discovery thatadding a contrasting agent (e.g, radiopaque agent) to an absorbablesponge provides for a material that not only facilitates hemostasis of abiopsy tract or other puncture wound but also permits preciseidentification of the site's location.

[0011] Accordingly, in one aspect, the invention is directed to a methodfor marking a bodily site in a patient that includes the steps of:

[0012] identifying the bodily site; and

[0013] positioning a pledget of absorbable sponge material adjacent thebodily site wherein the absorbable sponge material includes acontrasting agent.

[0014] With the present invention, the exact location of the bodily sitecan be located many weeks or longer following positioning of theabsorbable sponge material.

[0015] In another aspect, the invention is directed to a method forperforming a biopsy that included the steps of:

[0016] removing tissue from a vascular tissue site; and

[0017] positioning a pledget of absorbable sponge material adjacent thevascular tissue site wherein the absorbable sponge material includes acontrasting agent.

[0018] In another aspect, the invention is directed to a liquidpermeable, absorbable, gelatin sponge that is prepared by a process thatincludes the steps of:

[0019] (a) preparing an aqueous gelatin solution;

[0020] (b) adding an organic solvent in the aqueous gelatin solution toform a second solution;

[0021] (c) incubating the second solution;

[0022] (d) forming a foam from the second solution wherein a contrastingagent is added to the second solution at any step prior to forming thefoam; and

[0023] (e) drying the foam.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will now be described in greater detail withreference to the preferred embodiments illustrated in the accompanyingdrawings, in which like elements bear like reference numerals, andwherein:

[0025]FIG. 1 is a side cross sectional view of an adaptor for deliveryof a pledget to a needle;

[0026]FIG. 2 is a side cross sectional view of a syringe for connectionto the adaptor;

[0027]FIG. 3 is a side cross sectional view of an adaptor and syringecombination with a pledget positioned within the adaptor;

[0028]FIG. 4 is a side cross sectional view of the loaded adaptor andsyringe combination in preparation for connection to a biopsy needle;

[0029]FIG. 5 is a side cross sectional view of an alternative embodimentof an adaptor for delivery of a pledget including a template attached tothe adaptor;

[0030]FIG. 6 is a top view of the template as it is used for cutting apledget from an absorbable sponge sheet; and

[0031]FIG. 7 is a side cross sectional view of a portion of an organ anda system for delivering a pledget into a biopsy tract in the organ.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The present invention is directed to an absorbable spongematerial containing a contrasting agent. The absorbable sponge materialis delivered to a specific area or site in a patient (i.e., mammal)after a surgical or interventional procedure. For example, the spongematerial can be placed in the biopsy tract or other puncture wound andthe contrasting agent enables marking or identification of the area orsite. The absorbable sponge will be described in connection withtreatment of a biopsy tract after a percutaneous needle biopsy. Theabsorbable sponge material can also exhibit secondary benefits of, forexample, facilitating hemostasis and delivering therapeutic agents.

[0033] Prior to discussing the present invention in further detail, thefollowing terms are defined:

[0034] “Pledget” means a piece of absorbable sponge containing acontrasting agent preferably of a generally elongated shape having asize which allows injection in a hydrated state through a biopsy needleor other cannula.

[0035] “Sponge” means a biocompatible material which is capable of beinghydrated and is resiliently compressible in a hydrated state.Preferably, the sponge is non-immunogenic and is absorbable.

[0036] “Absorbable sponge” means a sponge which when implanted within apatient (i.e., human or other mammalian body) is absorbed by the body.The absorbable sponge contains a contrasting agent which may or may notbe absorbable. Besides the contrasting agent, the sponge can also beused to deliver a beneficial agent such as thrombin, radiation treatmentor the like.

[0037] “Bodily site ” means any tissue in a mammal where the absorbablesponge containing the contrasting agent can be introduced. The inventionis particularly suited for introducing the absorbable sponge into tissuesites where further treatment may be required, for example, as in thecase following biopsy.

[0038] “Hydrate” means to partially or fully saturate with a fluid, suchas, saline, water, or the like.

[0039] “Kneading” of the absorbable sponge material means both dry andwet manipulation of the sponge material which compresses, enlarges, orchanges the shape of the sponge material causing the sponge material tohave improved expansion response.

[0040] “Contrasting agent” means a biocompatible material that iscapable of being detected or monitored by fluoroscopy, X-rayphotography, CAT scan, ultrasound, or similar imaging techniquesfollowing placement into a mammalian subject. Preferred contrastingagents are radiopaque materials. The contrast agent can be either watersoluble or water insoluble. Examples of water soluble contrast agentsinclude metrizamide, iopamidol, iothalamate sodium, iodomide sodium, andmeglumine. Examples of water insoluble contrast agents include tantalum,tantalum oxide, and barium sulfate, each of which is commerciallyavailable. Other water insoluble contrast agents include gold, tungsten,and platinum powders. Some radiopaque contrasting agents are availablein liquid form. These include, for example, OMNIPAQUE from Nycomed,Inc., Princeton, N.J. Preferably, the contrast agent is water insoluble(i.e., has a water solubility of less than 0.01 mg/ml at 20° C.).

[0041] The absorbable sponge material of the present invention ispreferably a liquid permeable, water insoluble gelatin based sponge thathas contrasting agent incorporated in the matrix of the sponge. By“incorporated” is meant that the contrasting agent is substantiallydispersed throughout the sponge so that the contrasting material is notsimply found on the periphery of the sponge. The sponge is made bymixing a suitable organic solvent (e.g., formaldehyde) with an aqueoussolution of gelatin. The organic solvent facilitates the cross linkageof gelatin polymers. It is expected that glutaraldehyde may also besuitable. The resulting solution is then incubated typically at slightlyabove room temperature (30°-40° C.). Subsequently, a contrasting agentis added and the resulting mixture beaten to produce a firm foam.Thereafter, the foam is dried to produce the absorbable sponge material.

[0042] Typically, the aqueous gelatin solution containing 3-10% gelatinby weight is prepared as a warm solution (e.g., 80° C.) to help dissolvethe gelatin. The solution is then allowed to cool (e.g, 35°-40° C.)before the organic solvent is added. A preferred organic solvent isformalin (an aqueous solution of formaldehyde) . The amount of formalinused will control the hardness of the sponge and its rate of absorptioninto the body. The more formalin used, the harder the sponge and thelower the absorption rate. Typically, the amount used is between 0.01 to10% based on the gelatin solution. The beating or whipping process takesabout 5-15 or more minutes to produce a firm foam of about 4 to 8 timesthe volume of the original solution. The drying process initially beginswith oven drying in the presence of circulating air at about 30° to 33°C. or higher and 10% humidity. After the foam is thoroughly dried, thefoam can be heated to an elevated temperature of about 140° C. for asufficient length of time (e.g., 3 hrs) until the sponge is firm.Suitable absorbable sponge materials are further described in U.S. Pat.No. 2,465,357 which is incorporated herein by reference.

[0043] It has been found that at least for contrasting agents that arenot soluble in water, the contrasting agent must be added prior tobeating the gelatin/formalin solution. The reason is that once the foammaterial is produced, the contrasting agent cannot be incorporated intothe matrix of the sponge.

[0044] When employing contrasting agents that are liquids it ispreferred that they be added to the gelatin/formalin solution prior tobeing beaten to form the foam product. This will insure that thecontrasting agent is dispersed throughout the sponge.

[0045] Care should be taken when using insoluble contrasting agents notto overload the absorbable sponge material by using excessive amounts ofcontrasting agents. This will possibly result in sponges that havereduced cell structures, that is, the final volume will be significantlyless than if no contrasting agent was used.

[0046] Following the above formulation, absorbable sponge materialscontaining different amounts of contrasting agent were prepared andtested. Specifically, 5 grams of pork gelatin (Bloom value 275) weremixed in 100 grams of water at 80° C. and the solution was allowed tocool to 35° C. before 0.03 cc of 40%. formalin was added. The resultingsolution was incubated at 35° C. for 2 hours before tantalum powder (50to 150 grams) was added. The liquid was then vigorously mixed in a maltmixer to produce a foam. The foam was then oven dried at 35° C. for 12hours.

[0047] The absorbable sponge material was examined with a fluoroscopeand found to be extremely visible. Moreover, placement of the spongematerial with contrasting agent in puncture sites of a swine modeldemonstrated that the absorbable sponge exhibited good hemostaticproperties as well.

[0048] The sponge material with contrasting agent of the presentinvention is particularly suited for biopsies and other percutaneousprocedures where knowledge of the site of initial treatment, e.g.,tissue removal, is important.

[0049] While the absorbable sponge material can be employed with anysuitable medical instrument, a preferred device and method forfacilitating hemostasis of a biopsy tract is described herein toillustrate use of the absorbable sponge material. The technique isfurther described in U.S. patent application Ser. No______ and bearsAttorney Docket No. 032005-030 filed on May 28, 1999, and entitled“Device and Method for Facilitating Hemostasis of a Biopsy Tract,” whichapplication is incorporated herein by reference.

[0050]FIG. 1 shows the adaptor 12 in which the pledget 18 is placed forhydration and for delivery through the biopsy needle 16. The adaptor 12allows pieces of absorbable sponge material with relatively large crosssections to be easily delivered through a biopsy needle 16 with a muchsmaller cross section. The adaptor 12 also functions to remove air fromthe pledget 18.

[0051] The adaptor 12 which delivers the hydrated pledget 18 to theneedle 16 includes a first end 30 having an annular lip 32 or femaleluer fitting for connection to the syringe 14. A second end 34 of theadaptor 12 has a male luer fitting 36 for connection to a biopsy needle16 or other cannula The luer fitting 36 includes a tapered externalsurface 38 and a retaining ring 40 with internal threads for receivingan annular lip of the biopsy needle. The adaptor 12 has an internallumen with a first diameter D₁ at the first end 30 and a second diameterD, at the second end 34. Between the first and second ends of theadaptor 12 a tapered section 42 of the adaptor provides a funnel forcompressing the hydrated pledget 18 prior to injection through thebiopsy needle 16 and needle hub 28.

[0052] The adaptor 12 may be formed in any known manner such as bymolding from a plastic material. Preferably, the adaptor 12 istransparent so that the pledget 18 can be viewed through the adaptor andthe user can visually monitor when the pledget is loaded within theadaptor and when the pledget has been delivered into the needle. Theadaptor lumen may be provided with a friction reducing coating forimproved delivery. The delivery fluid also reduces friction for improveddelivery by wetting the exterior surface of the pledget 18.

[0053] As shown in FIG. 2, the syringe 14 includes a male luer fitting46, a fluid chamber 48, and a plunger 50. The first end 30 of theadaptor 12 is connectable to the luer fitting 46 of the conventionalsyringe 14. The syringe 14 may be provided with a spring 52 forautomatic filling of the syringe 14 with a predetermined volume offluid.

[0054] The biopsy needle 16 used with the present invention ispreferably a co-axial biopsy needle, such as a bi-axial or a tri-axialbiopsy needle. A co-axial biopsy needle includes an outer needle orcannula through which a tissue sample is removed with a tissue scoop orother biopsy instrument. Once the tissue sample has been removed, theouter cannula remains in the patient as illustrated in FIG. 4. Althoughthe cannula for delivery of the sponge pledget has been described as abiopsy needle, the cannula may be a catheter, sheath, or any other typeof cannula.

[0055] A preferred method of facilitating hemostasis of a biopsy tractwill be described with reference to FIG. 3 which shows the loading andhydration of the pledget 18 within the adaptor 12. A pledget 18 is cutand placed within the adaptor 12 from the first end 30 of the adaptor.The syringe 14 is filled with a predetermined amount of fluid, such assaline, and is connected to the first end 30 of the adaptor 12 by theluer fitting 46. The plunger 50 of the syringe 14 is then depressedslowly causing fluid to pass into the adaptor 12, hydrating the pledget18, and filing the adaptor with a column of fluid. Care should be takento inject the fluid slowly to prevent the pledget from being ejected outof the second end 34 of the adaptor. Preferably, the user waits a fewseconds once the fluid is injected into the adaptor 12 until the pledget18 is adequately hydrated creating a lubricous surface on the pledget.The pledget 18 may expand within the adaptor to fill or nearly fill thelumen of the adaptor. The adaptor 12 with the pledget 18 hydrated withinthe proximal end is ready to inject the pledget into a biopsy tract tofacilitate hemostasis within the biopsy tract. The adaptor 12 may beloaded prior to beginning the biopsy procedure.

[0056] After the biopsy procedure has been completed, the outer sheathof the biopsy needle 16 through which the biopsy has been taken ismaintained in place within the biopsy tract, as shown in FIG. 4. Thebiopsy needle 16 provides preestablished targeting of the delivery sitefor delivery of the absorbable sponge pledget 18 and eliminates theuncertainty of re-access. The luer fitting 36 of the adaptor 12 isconnected to the biopsy needle hub 28, as illustrated in FIG. 4. Thebiopsy needle 16 is withdrawn a short distance, such as about 1 to 20mm, along the biopsy tract to provide space for the pledget 18 to bereceived in the biopsy tract. Additional fluid is then rapidly injectedby the syringe to move the pledget 18 into the biopsy needle 16. Whenthe adaptor lumen has been blocked by the hydrated pledget 18 which hasswelled within the adaptor, injection of additional fluid will push thepledget through the tapered section 42 of the adaptor. If the adaptorlumen has not been entirely blocked by the pledget 18, the venturieffect will help draw the pledget through the tapered section 42 of theadaptor. After the pledget 18 is moved to the biopsy needle 16, thepledget 18 is then delivered from the needle 16 to the biopsy tract byrapid injection of additional fluid by the syringe 14. The hydratedpledget 18 quickly expands upon delivery to fill the available space inthe biopsy tract to facilitate hemostasis and provide localizedcompression.

[0057] The absorbable sponge material of the present invention can beshaped into the required size by conventional means. Pledgets may be cutwith a punch or a stencil or template and knife. Once hydrated, thepledget 18 can be easily compressed to fit into a lumen having a smallercross sectional area than the original cross sectional area of thepledget. Additionally, the kneading of the hydrated pledget 18 duringdelivery encourages air trapped within the absorbable sponge to beexpelled and replaced with fluid, allowing rapid expansion upondelivery.

[0058] When delivering a pledget 118 of absorbable sponge material, itis important to deliver a desired amount of the sponge material using aminimum amount of fluid.

[0059] Pledgets 118 with increased cross sectional area proximal endsmay be prepared in a variety of manners. For example, if a pledget 118is prepared from a sheet of sponge material, the increased proximal masscan be achieved by cutting the pledget with an enlarged proximal end.Alternatively, the pledget 118 may be formed by folding, rolling,compressing, or otherwise manipulating the sponge material to thedesired shape. The proximal pledget mass may also be increased by addingseparate pieces of material to the proximal end of the pledget. Thisadditional material may be layered, wrapped, coiled or attached to thepledget in any other manner. The pledgets may also be formed by molding,bump extruding, dipping, or the like. The larger cross sectional areaproximal end is generally about 1.2 to 4 times the cross sectional areaof the distal end. In addition, the proximal end with the larger crosssection area preferably extends along about ⅛ to ¾ of the total pledgetlength.

[0060] The pledget 118 illustrated in FIG. 5 has been formed by cuttinga strip of material from an absorbable sponge sheet 20 with the aid ofthe template 122 as illustrated in FIG. 6. After the strip is cut, theproximal end of the strip is then folded back onto itself to form apledget 118 with an increased cross sectional area and material mass ata proximal end. One example of a preferred embodiment of a pledget fordelivery down a 20 gauge biopsy needle or cannula has a size ofapproximately 0.1×1.5×0.06 inches and is folded as illustrated in FIG. 5to an overall length of about 0.9 inches. Placing this pledget 118 in anadaptor 112 having a largest internal diameter of 0.125 inches allowsthe pledget to be delivered to a 20 gauge or larger biopsy needle. Othercommon biopsy procedures use an 18 gauge or larger biopsy needle througha slightly larger guide cannula and would receive a somewhat largerpledget. After taking a core sample and removing the biopsy needle fromthe cannula guide, a pledget 118 maybe delivered through the cannula tothe biopsy site. The pledget 118 for use in the system employing an 18gauge or larger biopsy needle may be formed from a strip which isapproximately 0.11 - 0.12 inches wide by about 3.125 inches long with athickness of about 0.06 inches and folded to an overall length of about2.2 inches. This pledget having a 28 which is attached to the distal endof the adaptor.

[0061] As described above, the pledget may be delivered to the biopsytract by holding the biopsy needle or cannula 16 stationary andinjecting the pledget through the biopsy needle. If additional pledgetsare to be delivered, the biopsy needle 16 is withdrawn a distancesufficient to accommodate an additional pledget and the additionalpledget is then injected.

[0062] An alternative method of delivering the pledget into the biopsytract includes withdrawing the biopsy needle or cannula 16 duringdelivery of the pledget 18 to deliver the pledget in an elongated trailwhich follows the biopsy tract. Placing the absorbable sponge materialin a trail which fills the entire biopsy tract provides the addedbenefit of providing hemostasis along the entire biopsy tract. This isparticularly helpful for stopping the bleeding of biopsy tracts inorgans which tend to have excessive bleeding such as the liver, kidney,spleen, and other vascular organs.

[0063] In order to achieve a trail of absorbable sponge material in thebiopsy tract, one method of the present invention involves the deliveryof the pledget into the biopsy needle by a predetermined amount offluid. The biopsy needle is then withdrawn at a velocity V while thepledget material is ejected from the biopsy needle at a velocity E withrespect to the biopsy needle. The velocity V at which the biopsy needleis withdrawn is equal to or less than the velocity E at which theabsorbable sponge material is delivered The control of injection offluid and withdrawal of the needle to achieve the desired trail ofabsorbable sponge material in the biopsy tract maybe controlled with aninjection controlling device.

[0064] According to an alternative embodiment as illustrated in FIG. 7,the adaptor may be used to deliver the pledget into the biopsy needle 16and then the adaptor is removed from the biopsy needle. A plunger orstylet 80 which is generally provided with the biopsy needle 16 forinserting the biopsy needle is then used to deliver the pledget from thebiopsy needle. As shown in FIG. 7, the biopsy needle extends through thetissue 84 and into the organ 86 for removal of a core of tissue. Afterbiopsy, the pledget is injected into the needle 16 and the plunger 80 isplaced within the biopsy needle so that a distal end of the plungerabuts the proximal end of the pledget 118. The plunger 80 is then heldstationary while the biopsy needle 16 is withdrawn from the biopsy site.The plunger 80 causes the pledget 118 to be delivered in a trail 88which fills the biopsy tract. The trail 88 preferably extends along theentire biopsy tract to or past a surface of the organ 86. The deliveryof the trail 88 of absorbable sponge material provides an advantage overthe delivery of discrete blobs of material because the trail is able toprovide hemostasis along the entire tract. In contrast, if a blob ofabsorbable sponge material is delivered within the tract at a depth of1-2 cm from the surface of the organs, this 1-2 cm of biopsy tract maycontinue to bleed significantly.

[0065] As an alternative to delivery of the pledget as a trail, thepledget may be delivered as a plug; To deliver a plug the plunger 80 isadvanced into the needle 16 pushing the pledget out of the distal end ofthe needle while the needle is held stationary. A combination ofdelivery of plugs and trails may also be used. The pledget material maybe delivered entirely within a single anatomical structure or may crosstwo or more anatomical structures such as an organ, surrounding tissueand facial layer.

[0066] In some instances it may be desirable to deliver multiplepledgets in spaced apart positions along the biopsy tract, particularlyfor a long biopsy tract. For delivery of additional pledgets, the biopsyneedle 16 is retracted a distance sufficient to provide a space toaccommodate an additional pledget 18 and the injection proceduredescribed above is repeated for the additional pledget(s). For aparticularly large biopsy site or cavity, additional pledgets 18 may beinjected beside an initially injected pledget until the cavity isfilled.

[0067] Although biopsy is most commonly performed by biopsy needle,biopsy may also be performed through other cannulas, such as catheters,long needles, endoscopes, or the like. The treatment procedure accordingto the present invention can be used for facilitating hemostasis ofpuncture wounds through different types of cannulas including needles,catheters, endoscopes, and the like. In addition, the treatmentprocedure and systems according to the present invention may be used todeliver absorbable or non-absorbable sponge for other therapys. Forexample, sponge may be delivered for cosmetic or reconstructive bulkingor for temporary or permanent intravascular embolization.

[0068] In addition to the contrasting agent, the absorbable spongepledget 18 may be used to deliver a beneficial agent, such as, thrombin,radiation treatment, or the like. The pledget can also be used todeliver therapeutic agents, such as radioactive isotopes for localizedtreatment of tumors, anti-cancer agents, antimetastatic agents, and thelike. Examples of anticancer agents include 5-fluorouracil, cisplatin,prednisone, and others described in U.S. Pat. No. 4,619,913 which isincorporated herein by reference. The absorbable sponge pledget 18 maybe presoaked with the beneficial agent for delivery to the biopsy tract.Alternatively, the pledget 18 may be hydrated with the beneficial liquidagent or the agent may be delivered to the pledget after the pledget isplaced within the biopsy tract.

[0069] A pledget formed of inventive absorbable sponge materialpreferably will be absorbed by the body within 1 to 6 weeks. However,the pledget material may be designed to provide different rates ofabsorption. If the contrasting agent employed is also absorbable, thecontrasting agent should be absorbed at approximately the same rate asthe sponge material. Where the contrasting agent is non-absorbable, itwill remain at the site.

[0070] While the invention has been described in detail with referenceto the preferred embodiments thereof, it will be apparent to one skilledin the art that various changes and modifications can be made andequivalents employed, without departing from the present invention.

What is claimed is:
 1. A method for marking a bodily site in a patientcomprising the steps of: identifying the bodily site; and positioning apledget of absorbable sponge material adjacent the bodily site whereinthe absorbable sponge material includes a contrasting agent.
 2. Themethod of claim 1 wherein the contrasting agent is water insoluble. 3.The method of claim 2 wherein the contrasting agent is selected from thegroup consisting of tantalum, tantalum oxide, barium sulfate, gold,tungsten, and platinum and mixtures thereof.
 4. The method of claim 1wherein the contrasting agent is water soluble.
 5. The method of claim 4wherein the contrasting agent is selected from the group consisting ofmetrizamide, iopamidol, iothalamate sodium, iodomide sodium, andmeglumine and mixtures thereof.
 6. The method of claim 1 wherein thesponge material comprises a gelatin based sponge.
 7. The method forperforming a biopsy comprising the steps of: removing tissue from avascular tissue site; and positioning a pledget of absorbable spongematerial adjacent the vascular tissue site wherein the absorbable spongematerial includes a contrasting agent.
 8. The method of claim 7 whereinthe contrasting agent is water insoluble.
 9. The method of claim 8wherein the contrasting agent is selected from the group consisting oftantalum, tantalum oxide, barium, sulfate, gold, tungsten, and platinumand mixtures thereof.
 10. The method of claim 7 wherein the contrastingagent is water soluble.
 11. The method of claim 10 wherein thecontrasting agent is selected from the group consisting of metrizamide,iopamidol, iothalamate sodium, iodomide sodium, and meglumine andmixtures thereof.
 12. A liquid permeable, absorbable gelatin sponge thatis prepared by a process that comprises the steps of: (a) preparing anaqueous gelatin solution; (b) adding an organic solvent in the aqueousgelatin solution to form a second solution; (c) incubating the secondsolution; (d) forming a foam from the second solution wherein acontrasting agent is added to the second solution at any step prior toforming the foam; and (e) drying the foam.
 13. The gelatin sponge ofclaim 12 wherein step (d) comprises whipping the second solution until afoam is produced.